Abstract Nearly 40% of adults over age 60 are obese. On average, these individuals spend over 10 hours a day sitting. This is a concern since emerging research shows higher sitting time is associated with worse cardiovascular and metabolic health. In fact, most obese older adults have comorbid cardiometabolic conditions. Interventions which can reduce sitting time in this high-risk population could improve health and lower health care costs. As such, more research is needed to develop interventions to effectively reduce sitting time among older obese adults. The proposed study will address this important goal and build on the promising results of our I-STAND randomized pilot study. This study found that a theory-based, multi-modal behavioral intervention which combined phone counseling and technology-based behavioral prompts was feasible, acceptable, and significantly reduced sitting time (-75 minutes/day in the intervention compared to control group, p < .01). Among those with elevated blood pressure at baseline, blood pressure also improved in two of our pilot studies. In short, we found that I-STAND warrants evaluation in a large randomized controlled trial. The current study will compare I-STAND to an attention-matched control intervention among participants over age 60, with obesity, and who sit more than 8 hours per day (N = 284). Both interventions include one in- person session and 9 follow-up phone calls. Experimental participants will also receive prompts for standing via wrist-worn technology and a home environment audit to identify modifications to improve standing time. All participants will be followed for 12 months. After 6 months, experimental participants will be re-randomized to receive either 5 additional booster calls or no further intervention, allowing us to assess the effects of the initial intervention and booster sessions. The primary outcomes will be reduction in sitting time as measured by a thigh-worn activPAL inclinometer and blood pressure. The secondary outcomes include changes in cardiometabolic risk factors (e.g. weight, lipids, fasting glucose). Mediators of significant treatment effects will also be explored. If effective, I-STAND could easily be implemented by health care systems to improve the health of older obese adults nationwide.